Composite elastic yarn and the process therefor



Feb. 15, 1966 M. STORTI 3,234,724

COMPOSITE ELASTIC YARN AND THE PROCESS THEREFOR Filed 001). 16, 1963 United States Patent 3,234,724 COMPOSITE ELASTIC YARN AND THE PROCESS THEREFOR Michael Storti, Barrington, R.I., assignor to Rohm & Haas Company, Philadelphia, Pa., a corporation of Delaware Filed Oct. 16, 1963, Ser. No. 316,601 12 Claims. (Cl. 57152) This application is a continuation-in-part of my copending application, Serial No. 293,661, filed on July 9, 1963.

This invention relates to a high bulk yarn having improved elastic characteristics and particularly to an elastic high bulk yarn having high power. The invention also relates to the process of producing such yarns.

It is known that elastic yarn capable of producing fabrics having a soft hand can be produced on conventional apparatus by combining an untwisted continuous filament, multi-filament yarn and an elastic thread that has been extended two or three times the length it has in the relaxed state. On relaxation of the elastic thread, the multi-filament yarn forms a loose, helical wrapping which simulates a textured or bulk yarn to some degree. Structures of this nature are disclosed in United States Patent 3,011,302.

It it also known that elastic yarns can be formed by spinning one or more rovings of staple fibers as a sheath about a stretched core of elastic thread so that when the composite yarn is relaxed, the sheath fibers bulge outwardly to present a high bulk effect. United States Patent 3,038,295 discloses structures of this nature.

Further, it is known that covered elastic yarns can be produced by helically wrapping a twisted thread of a fibrous material about a rubber core. It is also known to twist an untwisted yarn about a rubber core, which may be stretched during the operation, as described for example in United States Patent 2,076,270.

The major disadvantage of elastic yarns produced by piror art processes is that they have a tendency to kink or curl up when in a relaxed condition rendering them difficult to handle in conventional weaving and knitting apparatus. To solve this problem, the art has used either helical wrapping of an elastic core, which is expensive, or untwisted or substantially untwisted covering yarns as in United States Patents 2,076,270 and 3,098,347. The reason for using a covering yarn is, inter alia, to impart the hand, appearance and dyeability of the covering yarn to the composite yarn. When the covering yarn is restricted to substantially untwisted yarns, these purposes are, in part, defeated.

Accordingly, it is an object of the present invention to provide a truly balanced elastic yarn.

Another objectof the invention is to provide a simple method to provide a balanced elastic yarn easily adapted to conventional textile machinery and requiring a minimum of production steps.

A further object of the invention is to produce an elastic yarn covered by any of the conventional nonelastic fibers.

Again, an object of the invention is to produce a covered elastic yarn simply and easily with a conventional machine and materials whereby the optimum properties of both the elastic thread and non-elastic thread may be realized without sacrifice;

Yet again, an object of the invention is to produce a covered elastic yarn using normally twisted covering yarns and without the necessity of helically wrapping the covering yarn about the elastic core.

These and other objects of the invention are set forth more fully hereafter in the following description and drawing wherein the figure shows schematically apparatus for carrying out the method of the present invention.

Briefly, it has been discovered that the above objects 3,234,724 Patented Feb. 15, 1966 ice are realized by a composite yarn comprising a core of elastic thread plied with an even number of normally twisted yarns of non-stretchable nature, half of the normally twisted yarns having an S-twist torque and the other half having a Z-twist torque, one torque being greater than the other, the composite yarn being twisted in the other direction from the resultant torque of the normally twisted yarn a sufficient number of times per inch to produce a balanced composite yarn. The product may be easily produced on conventional machinery such as a down-twister as will be shown hereafter.

By normally twisted is meant that the yarn has a twist of at least about ten turns per inch prior to plying into the composite yarn of the invention. Untwisted or low twist yarns, such as those having a producers twist of about 0.52.5 turns per inch, blossom when plied with an elastic yarn. The maximum twist which may be imparted to the non-stretch yarns is not critical. Generally, the non-stretch yarn will not have a twist greater than about 30 turns per inch. It is preferred to ply the elastic fiber with non-stretch yarns having a twist of from about 15-25 turns per inch.

The elastic core component of the improved yarn may be made of any commercially available elastic fiber such as natural rubber or a synthetic elastomer such as poly- (butadienestyrene), poly(butadiene-arcylonitrile), cispolybutadiene, cis-polyisoprene, elastomeric polyesters, elastomeric vinyl polymers, elastomeric acrylic polymers, spandex, etc. Spandex fibers are particularly useful as elastic threads. Many elastomeric polyurethanes useful in preparing spandex fibers are known, some being described in patents such as US. 2,650,212, 2,953,839 and 2,957,852.

Preferably, the elastic fiber should be one which has good stability when exposed to high temperature and chlorine, for this will make fabrics made therefrom more resistant to deterioration when submitted to repeated washings and/ or dry-cleaning operations. One fiber having such special merit is known to be formed from an acrylonitrile-butadiene copolymer compounded as described in US. patent application Serial No. 265,610, filed March 18, 1963, and now abandoned.

Similarly, any non-stretch yarn may be used for the fibrous rovings plied with the elastic thread. Such yarns may be formed of continuous filament or of stable fiber. These yarns include those derived from rayon, cellulose acetate, cotton, wool, polyesters, polyamides such as nylon 6 and nylon 66, polymers and copolymers of acrylonitrile, etc. Although the covering yarns are nonstretch, it is not meant to imply by this term that the yarns are completely rigid with no give, On the contrary many non-stretch yarns, particularly those prepared from Wool and cotton, have a measurable degree of give or stretch. Rather, by the term non-stretch as used herein it is intended to exclude textured thermoplastic yarns, which yarns have a high degree of elongation or stretch. The instant invention is particularly suited to the production of composite elastic yarns from staple fibers of conventional materials and, in particular, the naturally-occurring fibers such as cotton and wool.

The composite yarns of this invention will normally. be formed into fabric while in a stretched state and will shrink to a portion of their woven dimension when removed from the weaving or knitting machine. The degree of shrinking will depend partly on the modulus of elasticity of the composite yarn and partly upon the tightness of the weave or stretch. The composite elatsic yarns of the invention are believed to be unique in that they are adapted to be used in either warp or fill. Heretofore, elastic fibers have been limited commercially to fill, the low tensile of the elastic threads preventing their successful use in the warp of stretch fabrics. Composite yarns of the invention containing an elastic fiber and a high strength non-stretch yarn, such as nylon, can be used in the warp. The construction of the yarns of this invention is such that the strength of the composite yarn is determined by the non-stretch yarn, i.e., in the instant invention the yarn may be constructed so that any breaking strain applied to the composite yarn is borne by the non-stretch yarn.

The drafting (i.e., elongation) of the elastic fiber prior to its combination in the composite yarn affects the properties of the composite yarn. Thus, the non-stretch yarns restrict the return of the elastic fiber, each type and denier of non-stretch reacting differently in the blend for retraction characteristics. The number of turns per inch in the composite yarn will also affect the retraction characteristics, a greater number of turns resulting in a greater percentage of retraction. As in conventionally covered elastic yarns, the modulus can also be controlled by varying the draft ratio. Thus assuming an elastic fiber has 200% elongation at dead stretch which is plied according to the invention at dead stretch to produce a composite yarn which relaxes to have 100% elongation, the resulting composite yarn elongates only 100% while the elastic thread imparts the modulus characteristics to the composite yarn of 200% elongation. Therefore, any degree of elongation can be used within the characteristic range of the elastic fiber to attain both the desired degree of elongation and the desired working modulus in the composite yarn.

The drawing represents a conventional plying machine modified to provide means to elongate the elastic thread prior to its being combined in the composite yarn. In the drawing, 11, 12, 14 and 15 represent supply packages of non-stretch yarn 21, 22, 24 and 25. Supply package 13 provides the elastic thread which passes through a suitable tensioning device 16 adjusted to provide the desired stretch to the elastic thread. The individual strands of non-stretch yarn pass through suitable guides, as may be needed, to rolls l7 and 18, and then to feed rolls 26 and 27. The combined yarns then pass through the pigtail guide 28 to the ring twister 29 and the take-up package 30.

As illustrated, four strands of non-stretch yarn are represented as being combined with one strand of elastic thread. In such a combination, two of the supply packages should have an S-twist torque and the other two a Z-twist torque. If desired, fewer or a greater number of strands of yarn may be combined, and in some circumstances, particularly when using a low denier elastic thread, a plurality of elastic threads may be employed.

To illustrate the invention, the following examples are given. A conventional down twister was threaded with one package of 500 denier spun rayon S-twisted 23 turns, one package of similar spun rayon to which 13 turns per inch of Z-twist had been imparted and one package of elastic thread. The elastic thread was an acrylonitrilemodified butadiene polymer containing approximately 30% acrylonitrile and compounded with a reinforcing filler prior to curing. The filler was an anhydrous pyrogenic silica and represented approximately one-third of the cured elastomer. The relaxed elastic thread had a denier of approximately 280. A device for applying tension was applied to the elastic thread and adjusted so as to cause a 200% elongation during the plying operation. The machine was operated to apply five turns per inch Z-twist to the composite yarn. The resulting yarn is completely balanced and is particularly useful as the fill in stretch fabrics.

In this same manner a yarn was prepared by plying one end each of an S-twist (40 turns) and a Z-twist (35 turns) non-stretch, 7O denier nylon-6 yarn with one end of 280 denier elastomer. The same elastomer was used as in the preceding example. The composite yarn was given five turns per inch (Z-twist). The resulting yarn is a balanced yarn having only a slight Z-twist similar to a producers twist and may be used in the warp of stretch fabrics.

Similarly a yarn was prepared by plying one end each of an S-twist (15 turns) and a Z-twist (25 turns) nonstretch count single cotton yarn with one end of 280 denier elastomer. The same elastomer was used as in the preceding examples. The composite yarn was given five turns per inch (S-twist). The resulting yarn is balanced and is useful in stretch fabrics where it is desired to duplicate the hand, appearance and dyeability of cotton.

While the examples illustrate the use of rayon, nylon and cotton in separate examples, it is understood that the various fibers may be blended to produce a composite yarn. Thus a cotton yarn and a polyester yarn may be plied with an elastic thread, or other combinations of fibers may be employed as desired.

The composite yarns of the invention are balanced yarns, i.e., they have no more than a producers twist. The amount of twist to be given to the composite yarn to produce a balanced yarn as herein described will vary with the twist of the non-stretch yarns and their denier or count.

The process of the invention, by permitting adequate twisting of the composite yarn, produces an interlocked product while avoiding the kinking tendency of prior art products. Further, since the non-stretch cover yarns are themselves twisted, they are easier to handle and process and give products completely duplicating the hand, appearance and dyeability of regular textiles using the same non-stretch yarns while at the same time possessing the stretch and modulus of the elastic yarn.

The composite yarns may be used in ways well known for the production of a wide variety of fabrics. They may be used to perform the function of the conventional elastic thread to impart a powerful retractive force to the knitted or woven fabric. Close-fitting apparel of a wide range of retractive force, tensile strength and appearance can be produced, as also can decorators and industrial fabrics.

While the method of the present invention has been illustrated in connection with a particular apparatus, it is to be understood that modifications may be made therein within the scope of the following claims.

What is claimed is:

1. A composite yarn comprising a core of elastic thread plied with an even number of normally twisted yarns of non-stretchable nature, half of the normally twisted yarns having an S-twist torque and the other half a Z-twist torque, one torque being greater than the other, the composite yarn being twisted in the other direction from the resultant torque of the normally twisted yarns a suflicient number of turns per inch to produce a balanced composite yarn.

2. A composite yarn according to claim 1 wherein said composite yarn has a producers twist.

3. A composite yarn according to claim 1 wherein said normally twisted yarns have at least ten turns per inch.

4. A composite yarn according to claim 1 wherein at least one of said normally twisted yarns is cotton.

5. A composite yarn according to claim 1 wherein at least one of said normally twisted yarns is wool.

6. A composite yarn according to claim 1 wherein at least one of said normally twisted yarns is rayon.

7. A composite yarn according to claim 1 wherein at least one of said normally twisted yarns is nylon.

8. A composite yarn according to claim 1 wherein at least one of said normally twisted yarns is of a different fiber than the other of said normally twisted yarns.

9. A composite yarn according to claim 1 wherein said core contains at least two elastic threads.

10. Process of forming an elastic yarn which comprises plying an elastic thread with an even number of normally twisted yarns of non-stretchable nature, half of the normally twisted yarns having an S-twist torque and the other half having a Z-twist torque, one torque being greater than the other, and imparting a number of turns per inch to the composite yarn to balance the latent torque from the normally twisted yarns.

11. A process according to claim 16 wherein the number of turns imparted to the composite yarn is sufiicient to give a producers twist to the said composite yarn.

12. A process according to claim 10 wherein said normally twisted yarns have at least 10 turns per inch.

References Cited by the Examiner UNITED STATES PATENTS Cote 57163 Foster 57140 Wang 57-152 Rupprecht 57-152 Masurel 57-144 X Bridgeman et al 57-452 MERVIN STEIN, Primary Examiner. 

1. A COMPOSITE YARN COMPRISING A CORE OF ELASTIC THREAD PLIED WITH AN EVEN NUMBER OF NORMALLY TWISTED YARNS OF NON-STRETCHABLE NATURE, HALF OF THE NORMALLY TWISTED YARNS HAVING AN S-TWIST TORQUE AND THE OTHER HALF A Z-TWIST TORQUE, ONE TORQUE BEING GREATER THAN THE OTHER, THE COMPOSITE YARN BEING TWISTED IN THE OTHER DIRECTION FROM THE RESULTANT TORQUE OF THE NORMALLY TWISTED YARNS A SUFFICIENT NUMBER OF TURNS PER INCH TO PRODUCE A BALANCED COMPOSITE YARN. 